snd_sdl.c

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/*
Copyright (C) 2004 Andreas Kirsch
 
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
 
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 
See the GNU General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
*/
#include <math.h>
#include <SDL.h>
 
#include "darkplaces.h"
#include "vid.h"
 
#include "snd_main.h"
 
 
static unsigned int sdlaudiotime = 0;
static int audio_device = 0;
 
 
// This function is called when the audio device needs more data.
// Note: SDL obtains the device lock before calling this function, no need to lock it here.
static void Buffer_Callback (void *userdata, Uint8 *stream, int len)
{
    unsigned int factor, RequestedFrames, MaxFrames, FrameCount;
    unsigned int StartOffset, EndOffset;
 
    factor = snd_renderbuffer->format.channels * snd_renderbuffer->format.width;
    if ((unsigned int)len % factor != 0)
        Sys_Error("SDL sound: invalid buffer length passed to Buffer_Callback (%d bytes)\n", len);
 
    RequestedFrames = (unsigned int)len / factor;
 
    if (snd_usethreadedmixing)
    {
        S_MixToBuffer(stream, RequestedFrames);
        if (snd_blocked)
            memset(stream, snd_renderbuffer->format.width == 1 ? 0x80 : 0, len);
        return;
    }
 
    // Transfert up to a chunk of samples from snd_renderbuffer to stream
    MaxFrames = snd_renderbuffer->endframe - snd_renderbuffer->startframe;
    if (MaxFrames > RequestedFrames)
        FrameCount = RequestedFrames;
    else
        FrameCount = MaxFrames;
    StartOffset = snd_renderbuffer->startframe % snd_renderbuffer->maxframes;
    EndOffset = (snd_renderbuffer->startframe + FrameCount) % snd_renderbuffer->maxframes;
    if (snd_blocked)
        memset(stream, snd_renderbuffer->format.width == 1 ? 0x80 : 0, len);
    else if (StartOffset > EndOffset)  // if the buffer wraps
    {
        unsigned int PartialLength1, PartialLength2;
 
        PartialLength1 = (snd_renderbuffer->maxframes - StartOffset) * factor;
        memcpy(stream, &snd_renderbuffer->ring[StartOffset * factor], PartialLength1);
 
        PartialLength2 = FrameCount * factor - PartialLength1;
        memcpy(&stream[PartialLength1], &snd_renderbuffer->ring[0], PartialLength2);
 
        // As of SDL 2.0 buffer needs to be fully initialized, so fill leftover part with silence
        // FIXME this is another place that assumes 8bit is always unsigned and others always signed
        memset(&stream[PartialLength1 + PartialLength2], snd_renderbuffer->format.width == 1 ? 0x80 : 0, len - (PartialLength1 + PartialLength2));
    }
    else
    {
        memcpy(stream, &snd_renderbuffer->ring[StartOffset * factor], FrameCount * factor);
 
        // As of SDL 2.0 buffer needs to be fully initialized, so fill leftover part with silence
        // FIXME this is another place that assumes 8bit is always unsigned and others always signed
        memset(&stream[FrameCount * factor], snd_renderbuffer->format.width == 1 ? 0x80 : 0, len - (FrameCount * factor));
    }
 
    snd_renderbuffer->startframe += FrameCount;
 
    if (FrameCount < RequestedFrames && developer_insane.integer && vid_activewindow)
        Con_DPrintf("SDL sound: %u sample frames missing\n", RequestedFrames - FrameCount);
 
    sdlaudiotime += RequestedFrames;
}
 
 
/*
====================
SndSys_Init
 
Create "snd_renderbuffer" with the proper sound format if the call is successful
May return a suggested format if the requested format isn't available
====================
*/
qbool SndSys_Init (snd_format_t* fmt)
{
    unsigned int buffersize;
    SDL_AudioSpec wantspec;
    SDL_AudioSpec obtainspec;
 
    snd_threaded = false;
 
    Con_DPrint ("SndSys_Init: using the SDL module\n");
 
    // Init the SDL Audio subsystem
    if( SDL_InitSubSystem( SDL_INIT_AUDIO ) ) {
        Con_Print( "Initializing the SDL Audio subsystem failed!\n" );
        return false;
    }
 
    // SDL2 wiki recommends this range
    buffersize = bound(512, ceil((double)fmt->speed * snd_bufferlength.value / 1000.0), 8192);
 
    // Init the SDL Audio subsystem
    memset(&wantspec, 0, sizeof(wantspec));
    wantspec.callback = Buffer_Callback;
    wantspec.userdata = NULL;
    wantspec.freq = fmt->speed;
    wantspec.format = fmt->width == 1 ? AUDIO_U8 : (fmt->width == 2 ? AUDIO_S16SYS : AUDIO_F32);
    wantspec.channels = fmt->channels;
    wantspec.samples = CeilPowerOf2(buffersize);  // needs to be a power of 2 on some platforms.
 
    Con_Printf("Wanted audio Specification:\n"
                "    Channels  : %i\n"
                "    Format    : 0x%X\n"
                "    Frequency : %i\n"
                "    Samples   : %i\n",
                wantspec.channels, wantspec.format, wantspec.freq, wantspec.samples);
 
    if ((audio_device = SDL_OpenAudioDevice(NULL, 0, &wantspec, &obtainspec, SDL_AUDIO_ALLOW_FREQUENCY_CHANGE | SDL_AUDIO_ALLOW_CHANNELS_CHANGE)) == 0)
    {
        Con_Printf(CON_ERROR "Failed to open the audio device! (%s)\n", SDL_GetError() );
        return false;
    }
 
    Con_Printf("Obtained audio specification:\n"
                "    Channels  : %i\n"
                "    Format    : 0x%X\n"
                "    Frequency : %i\n"
                "    Samples   : %i\n",
                obtainspec.channels, obtainspec.format, obtainspec.freq, obtainspec.samples);
 
    fmt->speed = obtainspec.freq;
    fmt->channels = obtainspec.channels;
 
    snd_threaded = true;
 
    snd_renderbuffer = Snd_CreateRingBuffer(fmt, 0, NULL);
    if (snd_channellayout.integer == SND_CHANNELLAYOUT_AUTO)
        Cvar_SetValueQuick (&snd_channellayout, SND_CHANNELLAYOUT_STANDARD);
 
    sdlaudiotime = 0;
    SDL_PauseAudioDevice(audio_device, 0);
 
    return true;
}
 
 
/*
====================
SndSys_Shutdown
 
Stop the sound card, delete "snd_renderbuffer" and free its other resources
====================
*/
void SndSys_Shutdown(void)
{
    if (audio_device > 0) {
        SDL_CloseAudioDevice(audio_device);
        audio_device = 0;
    }
    if (snd_renderbuffer != NULL)
    {
        Mem_Free(snd_renderbuffer->ring);
        Mem_Free(snd_renderbuffer);
        snd_renderbuffer = NULL;
    }
}
 
 
/*
====================
SndSys_Submit
 
Submit the contents of "snd_renderbuffer" to the sound card
====================
*/
void SndSys_Submit (void)
{
    // Nothing to do here (this sound module is callback-based)
}
 
 
/*
====================
SndSys_GetSoundTime
 
Returns the number of sample frames consumed since the sound started
====================
*/
unsigned int SndSys_GetSoundTime (void)
{
    return sdlaudiotime;
}
 
 
/*
====================
SndSys_LockRenderBuffer
 
Get the exclusive lock on "snd_renderbuffer"
====================
*/
qbool SndSys_LockRenderBuffer (void)
{
    SDL_LockAudioDevice(audio_device);
    return true;
}
 
 
/*
====================
SndSys_UnlockRenderBuffer
 
Release the exclusive lock on "snd_renderbuffer"
====================
*/
void SndSys_UnlockRenderBuffer (void)
{
    SDL_UnlockAudioDevice(audio_device);
}
 
/*
====================
SndSys_SendKeyEvents
 
Send keyboard events originating from the sound system (e.g. MIDI)
====================
*/
void SndSys_SendKeyEvents(void)
{
    // not supported
}